Investigators looking into the financial collapse in Cyprus say key data about Greek bond purchases is missing from the country's biggest lender.

A report by professional services firm Alvarez & Marsal said a "mass deletion of data" had been found on one computer.

The missing data relates to Greek bonds the bank purchased, which turned into losses of almost $2.5 billion during the Greek debt crisis.

"Based on an initial review of the data, our computer forensic technologists have found that the computers of two employees ... have had wiping software loaded which is not part of the standard software installations at the Bank of Cyprus," the report said.

It is not clear yet whether the wiping of records was accidental or deliberate.

Victoria's laws for disclosing political donations have long been criticised as among the weakest in the nation, but Premier Daniel Andrews says his proposed reforms will make the state's donations laws "the strictest donation laws in the country".